Free film sleeved valve in multiwall bag



Sept. 10, 1968 J. H. LESSARD FREE FILM SLEEVED VALVE IN MULTIWALL BAG Fi led Aug. 16, 1965 2 Sheets-Sheet 2 FIG. 3

INVENFOQ m m H-LESSRQQ m ,n g TMML United States Patent 6 Claims. (cl. 229-625) ABSTRACT OF THE DISCLOSURE Multilayer pasted end paper bags are adapted for filling and subsequent closure through one corner thereof. A free-filmed sleeved valve is provided for ease of filling and subsequent sealing to prevent sifiting'of the material. The valve consists of a sheet of synthetic thermo-plastic material such as polyethylene or polypropylene which lies between two plies of the bag protruding therefrom sufficiently to form a free-filmed sleeve.

This invention relates to improvements in valve bags. More particularly, it is directed to an improved, free-filmsleeved valve in a pasted-end multiwall bag.

Valve bags having a plastic sheet material as a sleeve therefor are now well-known. One method for providing a free film sleeve in the valve opening of a pasted bottom multiwall bag involves first laminating a tube formed of polyethylene film and kraft paper, usually with a latex adhesive. One half of the outside circumference of such polyethylene tube must be adhered to the kraft multiwall bag. Since good paper-polyethylene adhesion is necessary to assure that the sleeve will not be displaced during the filling operation, a latex adhesive has generally been used.

Furthermore because of the tendency for latex adhesive to cause discoloration through white kraft paper and also because of added cost, a conventional paste is used in the bottom folding and scaling operation. Thus, the latex adhesive meets the paste adhesive at the bottom fold lines. Because of the chemical qualities of the two different adhesives, degradation takes place along the paste contact line. This abrogates the sift-proof qualities intended in the sleeved valve bag.

An object of one aspect of the present invention is the provision of a free film sleeved valve in a pasted-end multiwall bag in which the risk of loss of sift-proof qualities is minimized.

An object .of another aspect of the present invention is the provision of a simplified method for providing an improved free film sleeved valve in a pasted-end multiwall bag.

By one broad aspect of the present invention there is provided in a valve construction formed in a multiwall valve bag adapted to be filled by a filling spout extending into said valve, said construction including a valve opening and a flap for closing said opening, the provision of an interplied supplementary free sheet .of synthetic thermoplastic material disposed between two plies of said bag and extending at least partially along the length of said bag, said sheet being at least the width of said valve, said sheet extending along a portion of the width of said bag along a closed end thereof adjacent to said valve, whereby, when said valve is opened, said sheet overlies an outer wall of said bag adjacent to said valve.

By another aspect of the present invention there is provided a method for the provision of a free film sleeved valve in a pasted-end multiwall bag which comprises inserting a synthetic thermoplastic material sheet between ice two plies of paper comprising a multiply paper bag blank so that said sheet extends approximately equally on each side .of a side fold line of said blank adjacent said valve, said sheet being of a width approximately equal to the width of said valve, said sheet also extending beyond one marginal edge of said blank by an amount representative of a portion of the width of said bag.

In the accompanying drawings,

FIG. 1 is an isometric idealized view of the multiply valve bag of the present invention in its semi-blank form, showing the free film sleeve and a pair of plies between which it is disposed,

FIG. 2 is a plan view of a multiply tube adapted to form the multiwall bag of the present invention,

FIG. 3 is a plan view of an open'bag bottom before folding into the multiwall bag of the present invention,

FIG. 4 is an isometric view of the valve bag of the present invention.

The multiply bag of the present invention is similar to multiply valve bags heretofore made. Accordingly, in reference to FIG. 1, the partially folded blank 10, folded along fold lines 11 and 12 to provide panel 13 and overlapping panels 14 and 15 may be either a single ply, in which case the bag would be a double ply bag, or may be a plurality of plies in which case the bag will be a multiwall bag. In addition, the blank 10 is shown in partially folded form, exploded from blank 16 for convenience only. The bag is formed in the conventional manner after the free film sleeve 17 has been inserted.

For convenience, blank 16 will be referred to as the outer ply and blank 10 will be referred to as the inner ply, even though the present invention embraces the use of the free film sleeve between any two plies and is not restricted to use between the two outer plies. Blank 16 is provided with conventional fold lines 18 and 19 whereby main panel 20, and overlapping panels 21 and 22 may be formed, and transverse fiold lines 23 and 24- for the purpose of providing a bottom closure. Diagonal fold lines 25, 26 and 27, 28 are conventional for providing a valve, and end closure respectively.

Superposed over fold line 18 and equidistant thereover is a free film sleeve 17, formed of synthetic thermoplastic material film, such as, for example, polyethylene or polypropylene. Film 17 extends beyond marginal edge 29 by an amount equal to at least one half the valve size.

FIG. 2 shows the multiply tube prior to its folding and bottom sealing. The valve 30 and the free film sleeve 17 are clearly shown.

FIG. 3 shows the disposition of the free film sleeve 17 upon preliminary valve-forming folding along diagonal fol-d line 25, 26 land 27, 28 but prior to bottom folding along transverse fold lines 23, 24.

FIG. 4 shows the bag in its sealed condition and more particularly shows valve 30.

In the method of production of the free film sleeve valve bag of the present invention the film 17 is drawn into the tubes formed by blanks 10 and 16 together with the parent paper webs forming blanks 10 and 16 so that the sheet is folded along its longitudinal centerline with the longitudinal folded edge 18 of the flat tube, at the side of the tube on which the valve is to be made. The film 17 is perforated in such a manner that at snap-off it will project beyond edge 29 the required distance. The film will be recessed within the multiwall bag by a similar distance. It is of course not essential that the free film sleeve extend that distance within the bag; however in commercial production this will be the case.

By the present invention, therefore, it is possible to use a conventional adhesive for the entire bottom pasting operation at the valve end of the bag. The procedure is improved since the insertion of the free film (itself an improvement over conventional free film tubes) takes place conventional paper sleeve at the botttoming operation. This obviates the previous pre-lamination operation of forming a composite of polyethylene and paper. This simplifies' the sleeve insertion at the bottoming machine.

vI claim:

1. In .a valve construtcion formed in a multiwal-l bag adapted to be filled by a filling spout extending into said valve, said construction including a valve opening and a flap for closing said opening, the provision of a unitary supplementary free sheet of synthetic thermoplastic material disposed between two plies of said bag and extending at least partially along the length of said bag, said sheet being at least the width of said valve, said sheet lying substantially fiat and extending along a portion of the width of laclosed end of the bag adjacent to said valve, whereby, when said valve is opened, said sheet overlies an outer wall of said bag adjacent to said valve.

7 2. The bag of claim 1 wherein said film is polypropylene.

3. The bag of claim 1 wherein said film is polyethylene.

4. The bag of claim 1, wherein said film is disposed between the outer two plies of said m'ultiwalll bag.

.atathe tubingoperation, it is only necessary .to insert a i i method for the provision of a free film sleeved "valve int-a'pasted-end-multiwal1b ag which comprises inserting a synthetic thermoplastic material sheet between two plies of paper comprising a multiply paper bag blank so that said sheet extends approximately equal-1y on each side of a side fold line of said blank adjacent said valve, said sheet being at least the width of said valve, said sheet lalso extending beyond one marginal edge of said blank by an amount equal to a portion of the valve size.

6. The method of claim 5 wherein said film is disposed therein by. drawing a length of said film into the multiwall tube together with'the webs precursor to said walls.

References Cited UNITED STATES PATENTS 2,751,142. .,6/1956 .Williams 229-625 2,786,623 3/1957 Port 22962.5 2,791,160 5/1957 Burrell 22962.5 2,968,432 1/1961 Craigheas 22962.5 3,065,899 11/1962 Means et a1 2296 2.5

DAVID M. BOCKENEK, Primal Examiner. 

